Salted Caramel Kentucky Butter Cake

baking soda, half a teaspoon
half a teaspoon of salt
1 cup of chilled buttermilk
When making the Salted Caramel Sauce:
1 cup of sugar, granulated
6 tablespoons of finely chopped unsalted butter
1/2 cup of chilled heavy cream
half a teaspoon of sea salt, with a little more for topping
Flakes of sea salt, for garnishing